It is a highly advisable and almost universal practice to provide floor mats at the entrances to buildings to remove dirt from the footwear of persons entering the building. One form of entrance floor mat widely used in commercial and industrial buildings is based on rigid, elongated rails arranged parallel to each other and joined in closely spaced relation by a hinge-type coupling that enables the mat to be rolled up so that the floor or walk under it can be cleaned. The rails have tread surfaces, which may be ribbed or toothed metal or plastic elements, grit materials or carpet pieces, that assist in cleaning dirt from footwear. The dirt removed by the tread surfaces tends to fall or be scraped into the gaps between the rails. Floor mats of the type described above are disclosed in U.S. Pat. Nos. 3,808,628 (Betts, 1974); 4,029,834 (Bartlett, 1977); 4,568,587 (Balzer, 1986); Re. 32,061 (Ellingson, Jr., 1986) and European Pat. No. 0,067,024 (Parsons, 1986). Construction Specialties, Inc., the assignee of the present invention, ("CS") has marketed a floor mat very similar to the one described in the Bartlett '834 patent under the trademark "Turfmat." The CS "Turfmat" product has rails produced by extrusion from a rigid polyvinyl chloride (PVC) and having, therefore, rigid ball and socket type couplings. The CS "Turfmat" product also has integral ribs on each rail that are formed of a softer vinyl than the rest of the rail by coextrusion with the rigid vinyl of the rail bodies and coupling portions. The softer ribs provide a cushioning effect and also impart a non-slip property. While the "Turfmat" PVC mats have given reasonably good service and are less expensive than mats having aluminum rails, they are less durable than the aluminum mats.
The floor mats described in the Balzer '587 are currently marketed by Balco, Inc. (the assignee). The Balco mats have aluminum rails and "hinge members" formed of a relatively highly plasticized PVC, a flexible thermoplastic. The hinge members allow the mat to be rolled up by flexing throughout the extent of the transverse span between the aluminum rails and also by articulation at the ball and socket joints by which the hinge members are linked to the rails. Because the hinge members of the Balco mats have, like most mats of the rail type, holes to allow dirt and water to fall to the floor or other surface under the mat, the flexure of the PVC hinge members is concentrated at the segments that are aligned with the holes. The concentrated flexure is accompanied by increased stress. Under repeated flexure the highly stressed regions begin to fail. Eventually, an entire hinge member breaks apart, and the mat must be repaired or replaced.
The mats of the Parsons European patent have hinge members much like those of the Balco mats except that it is proposed that they be made of rubber. Stress concentration and fatigue failure are likewise a potential, though rubber should have greater durability than flexible PVC. However, rubber is generally more elastic than flexible PVC, and mats made according to the Parsons patent would probably be prone to transverse dimensional instability due to creaping of the rails toward or away from each other because of the elasticity of the rubber hinge members.
Assembly of the Balco and Parsons mats is tedious, because the hinge members are separate from the rails. For a given number of rails there are twice as many parts to be assembled by endwise sliding than in a mat in which the rail bodies are integral with the connector elements, such as the CS "Turfmat" and the CS "Pedimat" aluminum mats made according to the Bartlett '834 patent. Also, each rail has to be locked endwise to each hinge member, such as by rivets, and twice as many connections are required in the Balco mats as in the CS mats.